1. Field of the Invention
The present invention relates to a process for the production of pure fluorenone by oxidation of fluorene fractions with air or oxygen in the presence of quaternary salts.
2. Description of the Prior Art
According to K. Kinoshita, K. Okada and S. Hashimoto, Nippon Kagaku Zasshi 80, 206-8 (1959), it has been known to produce fluorenone in the liquid phase by air oxidation from fluorene in pyridine as a solvent and sodium hydroxide at about 95.degree. C. However, the process requires a cumbersome processing (working up) of the alkaline solution by treatment with acids and subsequent extraction with ether for obtaining the fluorenone. The yield is at most 50%.
In British Pat. No. 834,590, it has been proposed to oxidize fluorenone by oxidation of fluorene in propionic acid in the presence of cobalt bromide by passing over oxygen. The yield of fluorenone is given at 75%.
According to Y. Sprinzak, J. Am. Chem. Soc. 80, 5449-55 (1958), it has been known to treat fluorene in a pyridine solution in the presence of Triton B as catalyst with oxygen. However, production on an industrial scale would be uprofitable because of the required processing of the reaction product connected with large quantities of liquid for the isolation of the fluorenone as well as because of the consumption of fairly large quantities of pyridine.
German Pat. No. 1,262,268 teaches the production of fluorenone by catalytic oxidation of molten fluorene at an elevated temperature of about 150.degree. C. in the presence of stearates or resinates of manganese, cobalt and lead. This process requires special catalysts as well as the traditional measure of melting the fluorene. Moreover the yields, which do not exceed 50%, are not satisfactory.
According to T. Soboleva and V. A. Proskuryakow Zh. Prikl. Khm. (Leningrad) 1970, 43(8), it has furthermore been taught to obtain fluorenone by air oxidation of a fluorene emulsion in aqueous alkali at 175.degree. C. under pressure. However, this process requires a higher expenditure of power than is desirable.
Finally, it has also been taught in German published application No. 1,940,051 (priority of Aug. 6, 1969) to oxidize fluoren through the oxidation of fluorene in acetic acid in the presence of cobalt and manganese acetates as well as potassium bromide by passing over air. In this process too, the yields amount to only about 50%.
It is therefore a primary object of the present invention to provide a process for the production of pure fluorenone which is equally advantageous from both industrial and economic standpoints.